The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Recently, increase of oil price leads to a more competition to enhance fuel efficiency in automotive industry.
In this sense, research on an automatic transmission has been performed to simultaneously provide better drivability and fuel consumption by achieving more shift stages.
In order to achieve more shift stages for an automatic transmission, the number of parts is typically increased. This negatively affects installability, production cost, weight and/or power flow efficiency.
Therefore, in order to maximally enhance fuel efficiency and to lower manufacturing cost of an automatic transmission via multi shift stages, it is important to reduce number of parts of the transmission.
In this respect, an eight-speed automatic transmission has been recently introduced to perform more shift stages via planetary gear trains.
However, we have discovered that disclosed automatic transmissions of eight or more shift-stages includes a lot of components and thus may easily become lengthy.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.